This invention relates to a structure for detachably attaching to a rail a switchgear having two contactors mechanically and electrically joined with each other.
In the case of conventional structures of this kind, as shown in FIG. 1, a switchgear such as an integral electromagnetic contactor apparatus 21 comprises left and right electromagnetic contactors 22 and 23 mechanically and electrically integrally joined with each other. A movable hook 24 is slidably attached to each of the left and right electromagnetic contactors 22 and 23, respectively, and they are respectively biased by a spring (not shown) towards an unillustrated corresponding stationary hook attached to each contactor. Electric wiring is provided between the terminals of respective main contacts of the left and right electromagnetic contactors so as to open one main contact when the other main contact is closed.
When the electromagnetic contactor apparatus 21 is attached to a mounting rail 25, each movable hook 24 must be moved outwards against the elastic force of the spring to receive the rail 25 between the movable hooks 24 and the stationary hooks. Thereafter, when an operator takes his hand away from each movable hook 24, each movable hook 24 is urged by a spring toward its original position thereof so that the rail 25 is held between the movable and stationary hooks so that the electromagnetic contactors 22 and 23 are fit to the rail 25.
However, in such a conventional electromagnetic contactor apparatus, it is necessary to simultaneously move both of the movable hooks 24 outwards when the electromagnetic contactor apparatus 21 is attached and detached from the rail 25. It is not easy to manually move outwards both of the movable hooks 24 simultaneously, and therefore it is not easy to attach and detach the electromagnetic contactor apparatus 21 with respect to the rail 25.
In another conventional electromagnetic contactor apparatus, as shown in FIG. 2, a thermal relay 26 for preventing overheating of the apparatus is attached to the left electromagnetic contactor 22 for example, and there is wiring between the terminals of the respective main contacts of the left and right electromagnetic contactors 22 and 23 so as to open one main contact when the other main contact is closed. Such a thermal relay 26 does not allow an operator to simultaneously move outwards both the left and right movable hooks 24 attached to the left and right electromagnetic contactors 22 and 23, respectively.
When only one movable hook 24 is movably attached to either one of the electromagnetic contactors 22 and 23 to facilitate the attachment and detachment of the apparatus with respect to the rail, the strength of the hook is insufficient and the balance of the apparatus is lost when the apparatus is attached to the rail.